Enhancing pie chart with pointers - filling sectors of a circular X-Y gauge

  • Thread starter Thread starter David Powell
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D

David Powell

Belated thanks to Andy Pope for guidance on my problem, which was to
display two 'needles' on a circular chart - like a traditional
barometer - and to colour the sector appropriately.
This post is also to record the points I needed to understand, to
assist others.

1. 'Chart Type' belongs to a series, not the Chart. (This isn't
evident from the user interface, although I guess the pre-assigned
combination charts presented offer that promise.) So a pie chart and
an X-Y chart may be happily belong to the same chart object.

2. The axes of such a combination pie chart / X-Y chart are readily
aligned. E.g., if you assign the X-Y graph's axes' limits (both X and
Y) to (-1, +1), the centre will align with the pie graph's. You'd
hope so, I guess, but the hope is satisfied.

3. To draw a line which will align with the border of a pie sector,
use elementary circle trigonometry (x value related by cosine, y by
sine).
By convention, pie graphs start at '12 o'clock', whereas cartesian
angles increase anticlockwise from '3 o'clock', so subtract the
required angle from 90 degrees (or pi/2) before doing the trig and any
scaling.

4. Custom markers for the datapoints X-Y radial lines permit you to
add your own picture to plot around the circle.

Andy Pope's site would provide extra context.
(snip from Andy's early post 2003-06-01 09:16:19 PST)
Have a look at my examples of pic chart variations
(http://www.andypope.info/charts/pies.htm)

and also the gauge example
(http://www.andypope.info/charts/gauge.htm)

You maybe able to combine these techniques to get your desired result.
Click to expand...

David Powell.
 
David -

Sounds like my speedometer chart example:
http://www.geocities.com/jonpeltier/Excel/Charts/Speedometer.html

Andy and I often answer the same questions, but from different
directions. Sometimes when I'm pleased with myself for a certain
answer, I notice he's also responded, and I have to admire his solution
even more.

BTW, these are advanced observations you've made. Not easy for casual
users to understand.

- Jon
 
Jon's speedometer example illustrates points 1, 2 and part of 3 very well.
In fact, I have long had Jon's wider site bookmarked.
I may have failed to view Speedometer, assuming that it would be like John
Walkenbach's Clock.xls, which managed to confine itself to X-Y series.

Jon's site has the most complete attention to detail that I have seen, and I
commend his tutorials.
Explanations of charting really benefits from pictures, and he has been
meticulous in showing and describing every step, including "gotchas".
Let my time-pressured post serve as a keyword pointer for Usenet trawlers to
both his and Andy's resources.

(Andy had assisted me further outside this forum and I felt I should record
my learnings here.
The interpretation however is mine and not all observations are his.
The Excel self-assistance community is the most successful I have
encountered and I resolved to contribute before requesting again!)
 
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